SteamOS will be made available when the prototype hardware ships. It will be downloadable by individual users and commercial OEMs. (But unless you're an intrepid Linux hacker already, we're going to recommend that you wait until later in 2014 to try it out.) We'll post info soon about that. Oh, and stay tuned for the in-home streaming beta to begin soon, too!

I think everyone will be able to download the ISO, I think the 300 hardware beta testers will be US-only... which makes sense, there's a lot of hassle sending hardware overseas with any NDAs or what-not.

The only people affected are those 300 people who may have been chosen as a hardware beta tester, AFAICT.